Re: [Python-markdown-discuss] Overriding Functions, etc.

[Ben W. <da...@gm...>]

It's been a while since we discussed this (April), but I thought I'd
come back. I've looked at how PmWiki organizes the various markups as
compared to Markdown.

In response to my statement that PmWiki had an elegant, ad-hoc method
for adding new markup, Waylan said: "And not very pythonic. I remember
the first time I realized how PmWiki did some very OO like things
without OO code. For PHP it was amazing -
and a pleasure to work with. Especially considering PHP's OO sytax. Uhg!"

I've since taken the time to analyze how Patrick Michaud accomplished
this. Quite simply, he uses a hash-of-hashes to organize markup
relative to other markup (e.g., Strong before Emphasis). At
parse-time, he then passes this H-o-H through a custom heap algorithm
to divine the absolute parse order. I re-implemented his solution in
Python. It is very Pythonic since his custom heap exists in Python's
heapq library. This means the sorting is likely optimized in C. I
think Waylan "failed to see the forest for all of the trees" because
he allowed the confines of PHP to conceal the simple elegance of the
solution.

He also focused on the big-picture, which was PmWiki, and did not see
the small facet I was focusing on, which was markup management. What
Patrick solved was how to allow a developer simply to insert new
markup into a markup tree. Rather than extend the class, or mess with
the internals of class Markdown, Patrick's solution allows flexibility
in the class. The way Markdown is now, in order for me to add some
behavior I wanted, I had to tinker with Markdown class' internals.
Now, to add markup, all I need to do is tell my parser that I want it
to occur during inline, or even that it must occur before Emphasis.
Thus, for a wiki engine that allows developers to insert/change markup
by plug-in, the process is very OO. There's a reason Patrick is a PhD.
While PHP is inelegant, and Patrick's code is sometimes confusing, I
am constantly amazed at how he solves problems.

I invite you to consider PmWiki's Markup engine (specifically function
Markup(); and BuildMarkupRules();) The former instructs on how to
extend markup ad-hoc. The latter instructs how to take the resulting
heap and build a parse tree.

The only problem would be implementing this would not be backward
compatible. But, this is Pythonic as well, as the BDFL willingly
disregards tradition when warranted. It is not backward compatible
because it totally dismisses the present mechanism for ordering
markup. However, I think the gains are worth the cost.

Warm Regards,
Ben Wilson

On 4/10/07, Yuri Takhteyev <qar...@gm...> wrote:
> Just wanted to let you guys know that I am reading this, but don't
> have time to think about it seriously and respond this week.  However,
> from what I see so far, I think Ben identified a real problem and I
> would love it if you guys could come up with a solution that addresses
> most of the points that have been brought up so far.
>
> Ideally, this solution would maintain backwards compatibility with
> existing extensions.  If not, we can still put it in, but we'll have
> to think more carefully of when to release it and whether there should
> be a more general upgrade of how the extension mechanism works.
> (I.e., I think it's ok to change the extension framework once, but not
> every day.)
>
>   - yuri
>
> On 4/10/07, Waylan Limberg <wa...@gm...> wrote:
> >
> >
> > Ben Wilson wrote:
> > [snip]
> > > PmWiki has a situation where markups may be added willy-nilly while
> > > maintaining order. It would be rather radical to introduce to
> > > Markdown().
> >
> > And not very pythonic. I remember the first time I realized how PmWiki
> > did some very OO like things without OO code. For PHP it was amazing -
> > and a pleasure to work with. Especially considering PHP's OO sytax. Uhg!
> >
> > But if one tried to use PmWiki's approach in python, it would probably
> > be more work than it's worth. A subclass of dict which maintains order
> > or a class wrapping a list of tuples would be much less effort -- and
> > more pythonic. For that matter, it wouldn't all that difficult to build
> > a class from scratch for such a purpose.
> >
> > [snip]
> > > want the conversion to occur before/after/during another item. I
> > > mention PmWiki only because I'm very familiar with its approach and
> > > know its author seeks ease-of-customization. Markdown() generally does
> > > not mean to be as customizable as it follows the Markdown standard
> > > format.
> >
> > Ahh, now I know why your name seemed so familiar. Although I've been out
> > of the (PmWIki) loop for about a year now. It is true that Markdown does not
> > come close to PmWiki. If you're looking for more power, perhaps you
> > should look at reStructuredText [1]. It seems to be the python default
> > for markup, is easily extendable [2], and will output LaTex [3].
> > Personally, I prefer Markdown for its simplicity, but you seem to want
> > power which brings more complexity. Imo, using an establish markup
> > language (rest) is better than building your own custom creation.
> >
> > [1]: http://docutils.sourceforge.net/rst.html
> > [2]: http://docutils.sourceforge.net/docs/howto/rst-directives.html
> > [3]: http://docutils.sourceforge.net/docs/user/latex.html
> >
> > --
> > Waylan Limberg
> > wa...@gm...
> >
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>
> --
> Yuri Takhteyev
> UC Berkeley School of Information
> http://www.freewisdom.org/
>
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-- 
Ben Wilson
"Words are the only thing which will last forever" Churchill